This invention relates to a regulating valve with automatic release for regulating and limiting to a given value the pressure existing within a leak-tight pressure containment vessel, hereinafter designated as an enclosure.
In more exact terms, the invention relates to a regulating valve of the type comprising a moving element for effecting leak-tight closure of an opening formed in an enclosure by cooperating with a valve seating which forms part of said enclosure. One of the faces of said moving element is in contact with the enclosure fluid whilst a force is applied to the other face, said force being intended to balance a given pressure of the fluid corresponding to a threshold value which must not be exceeded.
It is pointed out that, in a regulating valve of this type, the moving element which serves to seal-off the enclosure is capable of displacement when the pressure within the enclosure exceeds a predetermined threshold value. The element accordingly moves from a first end position or bottom position in which it cooperates with the seating which is rigidly fixed to the vessel to a second end position or top position which is defined by a stop and in which said moving element is held away from said seating.
Regulating valves of the above-mentioned type which were designed prior to the present invention have a disadvantage in that they do not permit rapid upward displacement of the moving element to the top position when the pressure within the enclosure rises abruptly above the threshold value, thus entailing a potential danger of explosion of the enclosure.
Furthermore, regulating valves of this type do not lend themselves to a simple adjustment as a function of the pressure to be obtained within the enclosure.
The precise aim of the present invention is to provide a regulating valve which makes it possible to overcome the disadvantages stated in the foregoing.
The regulating valve with automatic release in accordance with the invention is of the type comprising a closure element adapted to move between a closed position in which it seals-off an opening formed in an enclosure and an open position in which it is withdrawn from said opening, means for exerting back-pressure on the closure element in order to maintain said element in its closed position when the pressure prevailing within the enclosure is lower than a given pressure. Said regulating valve is distinguished by the fact that the means for exerting back-pressure consist of a pneumatic jack which produces action on the closure element by means of a connecting system comprising coupling means which are capable of disconnecting the jack from the closure element in the event of a fast increase in the pressure which prevails within the enclosure.
The regulating valve which has the characteristic features outlined in the foregoing makes advantageous and profitable use of a pneumatic jack coupled with the moving element of the regulating valve by means of a mechanism for releasing said element in the event of fast variation in the difference between the pressures prevailing respectively within the enclosure and within the jack.
Thus the main advantage of the valve is to permit:
control of the displacements of the moving element by making it possible at each instant to carry out a suitable adjustment of the thrust exerted by the jack on said element;
a fast upward displacement of the moving element at the time of a sharp pressure rise within the enclosure, this being achieved as a result of uncoupling of the moving element and of the jack which constitutes an assembly having relatively high inertia;
adaptation of the displacement of the moving element to a wide range of rates of pressure rise within the enclosure;
maintaining of the enclosure in the depressurized state if necessary.
In accordance with the invention, the jack comprises an operating rod or so-called first rod extended by a sleeve in which is engaged one end of a second rod, the other end of which is rigidly fixed to the closure element. The coupling means comprise at least one ball housed within the wall of the sleeve and capable of engaging to a partial extent under the action of a calibrated spring within a groove formed in the second rod.
Moreover, each ball is preferably in contact with a push-rod which is guided in translational motion within a guide tube. One end of said guide tube is rigidly fixed to said sleeve whilst the other end is adapted to receive a screw which cooperates with a complementary screw-thread formed within the guide tube. The ends of said spring are applied respectively against said push-rod and against said screw.
In accordance with an advantageous arrangement of the invention, the regulating valve comprises a buffer storage tank connected on the one hand by means of a control valve to the zone of the jack cylinder which is delimited by the piston face remote from the closure element and, on the other hand, to a system for supplying compressed air at a given pressure.
When the ratio of respective volumes of the buffer storage tank and of the aforesaid jack zone is suitably chosen, the above-mentioned arrangement permits of suitable automatic adjustment of the thrust exerted by the jack.
In accordance with a further arrangement of the invention, those zones of the jack which are located on each side of the piston are connected to a buffer storage tank by means of a control valve for putting each zone into communication either with said storage tank or with the atmosphere, said buffer storage tank being connected to a system for supplying compressed air at a given pressure.
Furthermore, in accordance with one of the arrangements contemplated by the invention and mentioned in the foregoing, the jack cylinder zone delimited by that face of the piston which is remote from the closure element is connected to said buffer storage tank by means of a cock.
Thus the adjustment of the thrust exerted by the jack advantageously depends not only on the ratio of volumes of the buffer storage tank and of the jack but also on the pressure drop which is established across the cock and varies with the rate of pressure rise within the enclosure.
Further properties and advantages of the present invention will become more readily apparent from the following description of one exemplified embodiment which is given by way of illustration but not in any limiting sense and relates to a regulating valve in accordance with the invention.